Watson only knows what's in its databases, and can search it quickly. Siri can take voice input and use it for a keyword search on the web. They're very different, but of the two, Siri is affordable and more useful for the everyday needs of a person. No one really needs a pocket Watson.
That would be profoundly stupid if Watson wasn't programmed to search the internet as well as its own database to find answers to queries.
But yes I agree Watson [at least for now] isn't a viable economic choice for most people. I'm surprised that IBM hasn't tried to develop and market a competitor to Siri with the Watson interface.
Most of the android voice recognition systems don't hold a candle to Siri in my experience.